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The First Thousand Days: early, integrated and evidence-based approaches to improving child health: coming to a population near you?
  1. Jonathan C Darling1,
  2. Panagiotis D Bamidis2,3,
  3. Janice Burberry4,
  4. Mary C J Rudolf5
  1. 1 Division of Women's and Children's Health, University of Leeds School of Medicine, Leeds, West Yorkshire, UK
  2. 2 Leeds Institute of Medical Education, University of Leeds School of Medicine, Leeds, West Yorkshire, UK
  3. 3 School of Medicine, Aristotle University of Thessaloniki, Thessaloniki, Greece
  4. 4 Public Health (Children and Families) Adults and Health Directorate, Leeds City Council, Leeds, UK
  5. 5 Department of Population Health, Azrieli Faculty of Medicine, Bar-Ilan University, Ramat Gan, Israel
  1. Correspondence to Dr Jonathan C Darling, Division of Women's and Children's Health, University of Leeds School of Medicine, Leeds, West Yorkshire LS2 9JT, UK; J.C.Darling{at}


The ‘First Thousand Days’ refers to the period from conception to the child’s second birthday. It is increasingly gaining traction as a concept to guide public health policy. It is seen as a crucial window of opportunity for interventions that improve child and population health. This review outlines the origin and growth of the First Thousand Days concept, and the evidence behind it, particularly in the areas of brain development and cognition; mental and emotional health; nutrition and obesity; programming and economic benefits. The review then describes UK experience of use of the concept to inform policy, and a recent government inquiry that mandates more widespread implementation.

  • comm child health
  • health economics
  • general paediatrics

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Why this topic is important

  • Prevention and early intervention is better than cure

  • There is good evidence for many early interventions for child health, for example, immunisation, breast feeding.

  • Early life environment is important to later mental, physical and emotional health, for example, through programming, adverse childhood experiences.

  • The First Thousand Days is a potentially powerful concept to inform child health policy—it brings together compelling evidence that the period from conception to 2 years is foundational to later good health, and a critical window of opportunity.

You turn in amazement to the stranger with whom you have been talking for the past hour on the train. You had worked out she was a successful entrepreneur and philanthropist, but not at this scale. “You have how much to improve children’s health in this country?” She repeats the eye-watering amount of money. It could be truly transformative. “And you want me to tell you how to get the ‘biggest bang for your buck’?” You part company in 15 min. You desperately want to grasp this amazing opportunity. You close your eyes and think. The rhythm of the wheels on the tracks suddenly gives you the needed flash of inspiration as you recall a phrase from an article you read recently:

The First Thousand Days, The First Thousand Days…

The ‘First Thousand Days’ refers to the period from conception to the child’s second birthday. It is increasingly gaining traction as a concept to guide public health policy: a crucial window of opportunity to improve child (and population) health. The importance of early intervention is intuitive to paediatricians, but what is the evidence behind the First Thousand Days concept, and how useful is it as a tool to influence policy?

Origins of the First Thousand Days concept

The concept was launched in 2010 by the then US Secretary of State Hillary Clinton at an international conference on global child undernutrition. It has increasingly informed health policy in high-income countries including the UK, where in 2014 a cross-party manifesto brought further impetus under the banner ‘The 1001 Critical Days’.1 It has recently been the subject of a UK government consultation to which the Royal College of Paediatrics and Child Health (RCPCH) has contributed.2

What is the evidence for the importance of the First Thousand Days?

The First Thousand Days brings together a wealth of research to make the case that this period is foundational to later good health, and a critical ‘window of opportunity’, when the infant brain is particularly susceptible to influences, parents are especially receptive to advice and support and the developing child is most susceptible to harm from adverse environments.3 Healthy nutrition and development in this period are critical. Seminal contributions to the scientific basis for the importance of the very early years have been made by Mustard,4 Heckman et al 5 and Shonkoff et al.6

The WAVE report in 2013 presented compelling evidence-based recommendations for the first 1000 days to improve outcomes.1 3 Optimal early support for parents dramatically improves child development, and helps to avoid toxic stress that has later harmful impacts. This includes strategies to promote parent-child interaction and attachment, including parental awareness of emotional and nutritional needs of young children, and parents providing a rich language environment, including reading to children. Early intervention for at-risk children can enable effective support and intervention to prevent abuse and neglect, with long-term beneficial effects on later health and well-being.7 Interventions include effective maternal and infant mental health services, with an emphasis on early support, a well-trained workforce, integrated and responsive maternal and child health services and community enrichment, as through Children’s Centres.

Evidence for the importance of the first 1000 days will be considered under the following areas: programming (the developmental origins of disease); brain development and cognition; mental and emotional health; nutrition and obesity and economic benefits.


According to the well-evidenced Developmental Origins of Health and Disease concept (originally the ‘Barker hypothesis’), disadvantage in fetal life and early childhood is an important determinant of chronic disease in adulthood, in particular obesity, diabetes and heart disease.8 For example, low birth weight doubles the risk of diabetes and serious cardiovascular disease (eg, heart attack and stroke) by age 50 years.9 Mechanisms include: modifications to cytogenesis and organogenesis; changes to metabolic and endocrine responses and epigenetic effects which alter gene expression. The result is a ‘resetting’ or ‘tuning’ in early life to adapt to adversity, but with a long-term cost.

Brain development and cognition

Moore et al remind us that the brain is much more than a skull-encased set of neuronal connections, but is ‘embodied’ (intimately connected to, shaped by and influencing multiple body systems) and ‘emotional’ (emotions are an important organiser of brain development).10 Anything that adversely impacts brain development may have profound and far-reaching consequences as figure 1 shows. Babies have relatively few synapses at birth. Over the next few years, synapses develop and are refined by stimulation and experience. By the age of 6 years, ‘pruning’ starts ensuring that the most important networks of synapses grow (figure 2). The early neuroplasticity of the brain is both a strength (ability to adapt to the immediate environment) and a weakness (adaptations may have a long-term cost).10 Brain development can be adversely affected by suboptimal nutrition in early life for the reasons given above, but it is also affected by the emotional environment (secure attachment, toxic stress) and level of stimulation during this period.11

Figure 1

Abnormal brain development following neglect in early childhood. The CT scan of the brain of a healthy child aged 3 years (left) and a child aged 3 years suffering from severe sensory-deprivation neglect (right), showing microcephaly, enlarged ventricles and cortical atrophy. Reprinted with permission from Springer Nature: Brain and Mind, Perry BD 2002; 3:79-10011

Figure 2

Synaptic density in children at birth, 6 years and 14 years showing how synapses develop extensively in the early years and then undergo pruning to ensure the most important networks grow. Used with permission from Rethinking the Brain, New York. Families and Work Institute (1997).

Children whose development falls behind in the first year will struggle to catch up. Children under 2 years are more vulnerable to abuse and neglect, and the risk increases with substance misuse, domestic violence, mental illness and other complex family situations (which affect about a quarter of infants in the UK). A large randomised controlled trial of 233 families in Dublin found that a programme of positive parenting support from pregnancy through to age 4–5 years improved children’s development (cognitive, language, motor, social and emotional), approach to learning and their physical well-being compared with controls.12

Long-term follow-up of the well-evidenced Nurse Family Partnership programme demonstrates that early intervention results in improved academic achievement and fewer internalising mental health problems at age 12 years.7

Mental and emotional health

Since the seminal ‘Adverse Childhood Experiences’ study in 1998, evidence has continued to mount that early exposure to an adverse environment has widespread and long-lasting negative effects on mental as well as physical health.13–15 For example, lower birth weight is associated with depressive symptoms in adult life.14 Children born preterm and/or very low birth weight are more likely to have mental health and attention problems compared with peers, from childhood into adulthood.14 Early life experience, avoidance of toxic stress and ‘good-enough’ parenting, with the building of strong attachment bonds, is vital to later emotional and mental health.11

Nutrition and obesity

In 2008, a Lancet series called for a global health focus on pregnancy and the first 2 years.16 Effective interventions (eg, breastfeeding promotion, micronutrients) were highlighted that would reduce child morbidity and mortality. Progress was summarised in a further Lancet series in 2013, adding support for a focus on the first 1000 days.17 This demonstrated that effective implementation of 10 evidence-based nutrition interventions focused on young children and maternal health in at-risk countries, would reduce under-5 child deaths by 15%, stunting by 20% and severe wasting by 61%.

In high-income countries, nutrition in the first 1000 days (including maternal nutrition, obesity during pregnancy, breast feeding and early diet) has a powerful impact on later risk of obesity.18 Data from the National Child Measurement Programme show that 34.3% of children at age 11 years are overweight or obese.19 Obesity is hard to reverse once established; it is better prevented. Early intervention is key.20

A suboptimal nutritional environment (deficiency/excess of macronutrients and micro-nutrients) may have lifelong effects on brain development—the earlier this occurs, the greater and less reversible the impact.21

Economic benefits

According to the Nobel prize winning economist, Heckman, the best return on investment society can make is in the first 1000 days (figure 3).5 22 However, it is not a case of only investing early in life: investment in later childhood/adolescence maximises the chance of a good First Thousand Days for the next generation. The challenge in the current financial climate is how we can use life course data trajectories to measure effectiveness of interventions at an earlier stage. Tools such as the Early Development Instrument developed by Hertzman et al show promise, revealing links to early social and wider determinants of health.5 23 A ‘System Transformation’ approach, for example, as advocated by Halfon et al in the USA, may be a key to unlock progress through deeper understanding of the complex health and social systems within which early child health is situated.24

What is happening in the UK?

There is clear evidence for a First Thousand Days approach to investment and commissioning of maternity and children’s services. What about in practice, though? First Thousand Days is now guiding national UK strategy, following on from local programmes and investment in several parts of the UK.

UK government First Thousand Days consultation

The First Thousand Days Health and Social Care Committee inquiry outcome was published in early 2019 and reflects key points in the RCPCH submission.2 It mandates local authorities to improve First Thousand Days support through high-quality local services for children and families, incentivised by a transformation fund, and based on the following principles:

  • ‘proportionate universalism’—services for all but targeted according to need;

  • prevention and early intervention (with appropriate long-term, secure funding);

  • community partnerships;

  • meeting needs of marginalised groups;

  • greater integration and better multiagency working;

  • evidence-based provision.

A revised and expanded Healthy Child Programme is recommended, with increased health visiting resource, a wider family focus (not just the child, but those around the child), with preconception and pregnancy support. Although there is focus on the First Thousand Days, it is important that the programme is graded into later childhood, avoiding a ‘cliff edge’ loss of support. High-level goals are to reduce infant mortality; reduce adverse childhood experiences; increase school readiness and a focus on reducing child poverty and inequality. It calls for high-level leadership within government, joined-up working within government, and prioritisation of the First Thousand Days in policy and funding.

Initiatives in the UK

Leeds illustrates how the First Thousand days approach has informed difficult policy and funding choices in a climate of austerity, with priority given to early years investment (box 1).

Box 1

Leeds—a case study

The challenge

  • Central government funding to the City Council fell by nearly 60% (from £450 million to £184 million 2010–19).

  • Costs and demand for services increased, particularly due to growing/ageing population.

The response

  • The Council protected investment into early years services, informed by the First Thousand Days approach and evidence, and led by child public health professionals.

  • The Leeds Best Start Plan was developed to ensure a good start for every baby based on best evidence: through well-prepared, responsive parents; vulnerable families helped early by a skilled workforce; breaking of intergenerational cycles of abuse/violence.

  • Leeds has to date retained all Children’s Centres and largely maintained Health Visiting staffing levels.

The Best Start Plan

  • Priorities for implementation were developed through wide consultation with stakeholders (including a major conference).

  • These were implemented through greater integration of health visiting and Children’s Centres, with a suite of programmes and campaigns, eg:

    • Courses for parents in pregnancy and the first 2 years: some universal, others more targeted.

    • Universal observation attachment screen at 6–8 weeks check with ‘understanding your baby’ programme: infant mental health support where issues identified.

    • Courses delivered by a skilled multiagency workforce from Children’s Centres.

    • Baby Buddy’ app30 (see main text) customised for Leeds.

The Health Exercise and Nutrition for the Really Young (HENRY) programme

  • Implementation built on the pre-existing HENRY programme—an early life evidence-based preventative strategy for obesity25 running in Leeds since 2009.

  • Emphasis on enhanced practitioner effectiveness through proven models of working with families to effect behaviour change.

  • Includes an 8-week programme for parents that focuses on: parenting skills; healthy eating behaviour; nutrition; physical activity and emotional well-being.

  • Evaluation of available evidence for HENRY is positive, with significant impact on many aspects of family lifestyle likely to reduce risk of obesity.26

Obesity data

  • Latest data—obesity rates in Leeds have decreased significantly (9.4% to 8.8%) from 2009 to 2017 at age 4–5 years, especially in disadvantaged children, contrary to national trends.32

  • Although this does not demonstrate a causal link to the HENRY programme, it merits further investigation.

At its core is HENRY, a national initiative that trains community and health practitioners to work more effectively with parents of very young children to establish healthier home environments.25 26

Wales has been implementing a similar approach in some areas since 2011, and nationally since 2015 (under the title ‘F1000D’), underpinned by national policy drivers (such as the Well-being of Future Generations (Wales) Act 2015). A First Thousand Days collaborative has been set up, with system engagement events around the country. The programme has three key objectives: 1) optimal outcomes from every pregnancy for mother and child; 2) children achieving their developmental outcomes at age 2; 3) fewer children exposed to adverse childhood experiences in the first 1000 days.

Scotland has had over a decade of emphasis on early intervention, with an explicit government policy commitment in 2008,27

and innovative quality improvement approaches to facilitate better early child outcomes. Their Children and Young People Improvement Collaborative website illustrates the success of this approach with case studies.28

‘A Better Start’ is a 10-year, £215 million programme funded by the National Lottery. It commenced in 2015 with five partnership areas across the UK.29 It focuses on improved outcomes for young children, through investment in early childhood, co-design of services with families and stakeholders and sharing learning and solutions across the network and beyond.

A number of other regions and councils are now championing a First Thousand Days approach, for example, since 2017 Croydon and Calderdale councils.

The role of smartphone technology

Technological solutions are attractive because they may empower parents in their parenting role,30 can be easily scaled and to some extent can be co-created with local communities. They are unlikely to be effective on their own, but may best support face-to-face programmes (eg, alongside health visiting or parent groups).

Best Beginnings is a UK charity dedicated to improving the health and well-being of babies and young children in the UK by tackling inequalities through developing early years digital and other resources. Their award-winning Baby Buddy app supports parents through pregnancy, birth, parenting and beyond. They have adapted the app for different contexts, for example, Leeds and Cyprus. The app is reported to: increase parents’ confidence, skills, well-being; promote mother-infant attachment; reduce social isolation; support behaviour change (eg, one study showed a 9% increase in exclusive breast feeding).30 However, a recent randomised controlled trial reported no impact on maternal self-efficacy 3 months postbirth, but a post hoc analysis indicated improved breast feeding at 1 month.31


The First Thousand Days concept is a simple, evidence-based and persuasive message for potential funders and commissioners: that investment in the critical ‘first 1000 day window’ of children’s lives is worth it. The message is relevant in low-income and middle-income and high-income countries. Investment should not be only for the first 1000 days, but especially for that period, then grading out into later childhood. For UK paediatricians and parents, the recent First Thousand Days inquiry holds hope of change for the better—exactly how remains to be seen. Perhaps you might have a role in shaping it locally?



  • Correction notice This paper has been amended since it was published online. There is a factual error regarding the funding of the A Better Start programme. This sentence: ‘A Better Start’ is a 10-year, £215 million programme by the National Children’s Bureau, funded by the National Lottery' has been changed to ‘A Better Start’ is a 10-year, £215 million programme, funded by the National Lottery.'

  • Contributors JD wrote the first draft of the manuscript, drawing on documents written for Leeds City Council by JB. PDB, JB and MCJR all contributed to the final draft.

  • Funding The authors have not declared a specific grant for this research from any funding agency in the public, commercial or not-for-profit sectors.

  • Competing interests None declared.

  • Patient consent for publication Not required.

  • Provenance and peer review Commissioned; externally peer reviewed.

  • Data availability statement No data are available. Not applicable.